Recently, the United States Environmental Protection Agency has instituted stringent requirements for discharging or otherwise disposing of wastes into the environment. Therefore, commercial effluents (such as laundry wastewater) contain a variety of contaminants which can no longer be discharged into public sewers or fed into sewage treatment facilities.
State and local environmental protection agencies have adopted the federal standards and, in many cases, have even exceeded them in stringency. Therefore, it has become necessary for local industries to purify their wastewater or incur heavy fines and operating restrictions.
Among the industries most subject to the new regulations are commercial laundries, whose waste effluents are particularly afoul with contaminants such as fats, oils, greases, heavy metals, dirt, particulates, solids, etc. Laundry effluents inherently accumulate and concentrate these contaminants. Laundry wastewater is, in particular, closely monitored and regulated by environmental authorities.
In the past, commercial, industrial and institutional cleaning establishments removed oils and greases from textiles by applying detergents thereto. The wastewater was then discharged to the sewer or, in extreme cases, when necessary, treated.
No longer are those procedures for laundering textiles and discharging laundry wastewater effluents adequate. The extremely high standards presently imposed for allowable contaminants in discharged wastewater, cannot usually be met when utilizing the conventional, aforesaid techniques.
In addition, one of the major drawbacks of the prior method of processing the effluent is that it was essentially a batch process. This process is very slow, with the effluent remaining for an extended period of time in large holding tanks so that the FOGs could rise out of solution, before the skimming could be performed. Various mechanical and chemical means were utilized to froth or foam the emulsified contaminants in the wastewater, in order to assist their rise to the surface in the tank. More often than not, the foaming and frothing additives were themselves undesirable contaminants that leached into and polluted the dischargeable wastewater.
In sum, the previous procedure was generally costly and inefficient.
Given more recent regulations, the discharge effluents are now required to be relatively free of total petroleum hydrocarbons (TPHs), as well as the FOGs. This new requirement places an even greater demand on the ability of purification systems to separate the polluting substances from the waste effluent.
While particularly applicable to laundry waste effluent purification, the present invention can be applied to almost any type of industrial wastewater management problem.
The current invention can be used to treat waste effluents in car washes, truck wash facilities, oil dealer establishments, airplane washing operations and garages, as well as in commercial, industrial and institutional laundries.
The process of this invention is not heavily dependent upon time and/or gravity to separate the emulsion, as was necessary in the aforementioned prior art procedure. Rather, this invention chemically breaks down the emulsion so as to release the FOGs from the water phase. The effluent is acidified in order to cause dissolution of the alkaline emulsion and release of the FOGs from the water. To this acidified effluent is added an organic, cationic polymer, which acts as an agglomerating and/or coagulating agent. The acidified effluent is then fed through a coalescer, where the agglomerated FOGs are adsorbed upon an appropriate surface, e.g., a plate of lipophilic material, such as a polyvinylchloride or polypropylene media pack. The agglomerated oil molecules rapidly coalesce and gather upon this surface, forming droplets. The oil droplets quickly rise to the top of the effluent stream where they are siphoned off and/or pumped away. The addition of the organic, cationic polymer prior to the coalescing provides an agglomeration and/or a coagulation of FOGs in solution. This enhances and makes the coalescing procedure more efficient. Thus, the invention increases the ability to reduce the percentage of TPH from the waste effluent in order to meet the newer, more rigorous purification requirements.
One of the major advantages of the invention is that the treatment method can be performed as a continuous process, thereby eliminating the need for large holding tanks and time-consuming holding and storage procedures for effluents. Additionally, harmful and expensive foaming and frothing agents are not employed in this process.